1. Technical Field
The present invention relates to a secondary battery and, more particularly, to separated support tapes having an improved structure and attached to a lower portion of an electrode assembly in order to allow the electrode assembly to be easily inserted into a can of a prismatic type secondary battery.
2. Related Art
A secondary battery has an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly is accommodated in a can made from aluminum or an aluminum alloy, and an electrolyte is then injected into the can. In this state, the can is sealed, thereby forming the secondary battery. An electrode terminal insulated from the can is provided at an upper portion of the secondary battery in order to form a cathode or an anode of the secondary battery. If the electrode terminal is an anode, the can serves as a cathode, and if the electrode terminal is a cathode, the can serves as an anode. Safety devices, such as a PTC (positive temperature coefficient) device, a thermal fuse, and a PCM (protective circuit module), are connected to the secondary battery. Such safety devices are electrically connected to the anode and the cathode of the secondary battery in order to prevent the secondary battery from being damaged or broken by shutting off current applied to the secondary battery if the voltage of the secondary battery is suddenly increased due to overcharge or over-discharge. The secondary battery equipped with the safety devices is accommodated in a case, thereby forming a secondary battery pack.
A secondary battery includes an electrode assembly, a negative electrode tap, a positive electrode tap, and a single support tape. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate, and wound in the form of a jelly roll. The negative electrode tap electrically connected to the negative electrode plate and the positive electrode tap electrically connected to the positive electrode plate are upwardly withdrawn from an upper portion of the electrode assembly. The electrode assembly wound in the form of a jelly roll is accommodated in a can having a hexahedral shape and made of metal, such as aluminum.
A single support tape having a predetermined length and a predetermined width is attached to a lower portion of the electrode assembly in order to allow the electrode assembly to be easily inserted into the can when the electrode assembly in the form of a jelly roll is inserted into the can. The single support tape completely surrounds the lower portion of the electrode assembly except for predetermined marginal regions of about 1 to 2 mm formed at both lower sides of the electrode assembly.
However, when performing a safety test on the secondary battery while accommodating the electrode assembly in a can, the electrode assembly being provided at its lower portion with the single support tape, the following problems may occur:
Firstly, when performing a battery safety test by pressing both lateral portions of the battery in a widthwise direction thereof in order to evaluate the possibility of firing in the battery, a middle portion of the battery is bent as the battery is compressed, so that the battery is folded. At this point, due to provision of the single support tape supporting the lower portion of the electrode assembly, a wrinkle may occur at a middle portion of a lower half of the electrode assembly. Thus, the possibility of fire in the battery due to a hard short may increase.
Secondly, if the signal support tape strongly grips the lower portion of the electrode assembly, electrolyte cannot sufficiently flow into the lower portion of the electrode assembly, thereby deteriorating performance and/or battery capacity of the battery.
Thirdly, since the single support tape substantially covers the entire area of the lower portion of the electrode assembly, a large amount of single support tape is necessary, resulting in increased manufacturing cost of the battery. Moreover, the single support tape is necessary only to allow the electrode assembly to be easily inserted into the can, and the single support tape may be released from the electrode assembly after the electrode assembly has been inserted into the can if the signal support tape is weakly attached to the lower portion of the electrode assembly. Thus, such excessive usage of the single support tape must be reconsidered.